1. Field of the Invention
The present invention relates to hydroprocessing hydrocarbonaceous feeds using a combination of cocurrent and countercurrent liquid hydroprocessing stages and one vapor hydroprocessing reaction stage. More particularly the invention relates to catalytically hydroprocessing a hydrocarbonaceous feed in a first liquid reaction stage in which the feed and treat gas flow cocurrently to produce a liquid and vapor effluent which are separated, with the liquid then hydroprocessed in a second stage flowing countercurrently to the treat gas to produce a hydroprocessed product liquid at the bottom of the second stage and a vapor effluent at the top, with both vapor effluents combined and hydroprocessed in a vapor stage.
2. Background of the Invention
As supplies of lighter and cleaner feeds dwindle, the petroleum industry will need to rely more heavily on relatively high boiling feeds derived from such materials as coal, tar sands, shale oil, and heavy crudes, all of which typically contain significantly more undesirable components, especially from an environmental point of view. These components include halides, metals, unsaturates and heteroatoms such as sulfur, nitrogen, and oxygen. Furthermore, due to environmental concerns, specifications for fuels, lubricants, and chemical products, with respect to such undesirable components, are continually becoming tighter. Consequently, such feeds and product streams require more upgrading in order to reduce the content of such undesirable components and this increases the cost of the finished products.
In a hydroprocessing process, at least a portion of the heteroatom compounds are removed, the molecular structure of the feed is changed, or both occur by reacting the feed with hydrogen in the presence of a suitable hydroprocessing catalyst. Hydroprocessing includes hydrogenation, hydrocracking, hydrotreating, hydroisomerization and hydrodewaxing, and therefore plays an important role in upgrading petroleum streams to meet more stringent quality requirements. For example, there is an increasing demand for improved heteroatom removal, aromatic saturation, and boiling point reduction. In order to achieve these goals more economically, various process configurations have been developed, including the use of multiple hydroprocessing stages as is disclosed, for example, in European patent publication 0 553 920 A1 and U.S. Pat. Nos. 2,952,626; 4,021,330; 4,243,519; 4,801,373 and 5,292,428.